--
>
> Passes light testing (five rounds of kernbench) on an x86_64 box.
>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> ---
>
> include/linux/hardirq.h | 4 +++-
> kernel/irq/handle.c | 2 ++
> kernel/irq/manage.c | 25 +++++++++++++++++++++++++
> 3 files changed, 30 insertions(+), 1 deletion(-)
>
> diff -urpNa -X dontdiff linux-2.6.23-rc4-rt1/include/linux/hardirq.h linux-2.6.23-rc4-rt1-sairq/include/linux/hardirq.h
> --- linux-2.6.23-rc4-rt1/include/linux/hardirq.h 2007-09-20 17:34:52.000000000 -0700
> +++ linux-2.6.23-rc4-rt1-sairq/include/linux/hardirq.h 2007-09-20 18:35:53.000000000 -0700
> @@ -105,8 +105,10 @@
>
> #ifdef CONFIG_SMP
> extern void synchronize_irq(unsigned int irq);
> +extern void synchronize_all_irqs(void);
> #else
> -# define synchronize_irq(irq) barrier()
> +# define synchronize_irq(irq) barrier()
> +# define synchronize_all_irqs(irq) barrier()
> #endif
>
> struct task_struct;
> diff -urpNa -X dontdiff linux-2.6.23-rc4-rt1/kernel/irq/handle.c linux-2.6.23-rc4-rt1-sairq/kernel/irq/handle.c
> --- linux-2.6.23-rc4-rt1/kernel/irq/handle.c 2007-09-20 17:34:51.000000000 -0700
> +++ linux-2.6.23-rc4-rt1-sairq/kernel/irq/handle.c 2007-09-22 23:34:13.000000000 -0700
> @@ -150,7 +150,9 @@ irqreturn_t handle_IRQ_event(unsigned in
> do {
> unsigned int preempt_count = preempt_count();
>
> + rcu_read_lock();
> ret = action->handler(irq, action->dev_id);
> + rcu_read_unlock();
> if (preempt_count() != preempt_count) {
> stop_trace();
> print_symbol("BUG: unbalanced irq-handler preempt count in %s!\n", (unsigned long) action->handler);
> diff -urpNa -X dontdiff linux-2.6.23-rc4-rt1/kernel/irq/manage.c linux-2.6.23-rc4-rt1-sairq/kernel/irq/manage.c
> --- linux-2.6.23-rc4-rt1/kernel/irq/manage.c 2007-09-20 17:34:51.000000000 -0700
> +++ linux-2.6.23-rc4-rt1-sairq/kernel/irq/manage.c 2007-09-22 23:34:15.000000000 -0700
> @@ -45,6 +45,30 @@ void synchronize_irq(unsigned int irq)
> EXPORT_SYMBOL(synchronize_irq);
>
> /**
> + * synchronize_all_irqs - wait for all pending IRQ handlers (on other CPUs)
> + *
> + * This function waits for any pending IRQ handlers for this interrupt
> + * to complete before returning. If you use this function while
> + * holding a resource the IRQ handler may need you will deadlock.
> + * If you use this function from an IRQ handler, you will immediately
> + * self-deadlock.
> + *
> + * Note that this function waits for -handlers-, not for pending
> + * interrupts, and most especially not for pending interrupts that
> + * have not yet been delivered to the CPU. So if an interrupt
> + * handler was just about to start executing when this function was
> + * called, and if there are no other interrupt handlers executing,
> + * this function is within its rights to return immediately.
> + */
> +void synchronize_all_irqs(void)
> +{
> + if (hardirq_preemption)
> + synchronize_rcu(); /* wait for threaded irq handlers. */
> + synchronize_sched(); /* wait for hardware irq handlers. */
I don't undrestand the synchronize_sched part above. How does that wait
for all hardware irq handlers? Wouldn't the synchronize_rcu be sufficient?
-- Steve
> +}
> +EXPORT_SYMBOL_GPL(synchronize_all_irqs);
> +
> +/**
> * irq_can_set_affinity - Check if the affinity of a given irq can be set
> * @irq: Interrupt to check
> *
> @@ -886,3 +910,4 @@ void __init early_init_hardirqs(void)
> for (i = 0; i < NR_IRQS; i++)
> init_waitqueue_head(&irq_desc[i].wait_for_handler);
> }
> +
> -
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